Abstract: An area limit control part as a control section outputs a requested boost pilot pressure for driving a control valve, based upon a pilot pressure in accordance with an operating amount of an operating lever and a posture signal of a posture sensor. A drive permission determination part determines whether or not a drive of a hydraulic actuator is permitted based upon the pilot pressure in accordance with the operating amount of the operating lever. A pilot pressure selecting part selects the requested boost pilot pressure from the area limit control part in such a manner as to drive the control valve with the requested boost pilot pressure to the hydraulic actuator the drive of which is permitted, and not to drive the control valve to the hydraulic actuator the drive of which is not permitted.

Abstract: Provided is a work machine capable of regenerating a return hydraulic fluid from a hydraulic actuator while preventing a drag loss of a regeneration hydraulic motor and a hydraulic pump from increasing and preventing the regeneration efficiency of the regeneration hydraulic motor from decreasing. A controller 100 computes a required regeneration hydraulic motor revolution speed from a displacement of a regeneration hydraulic motor 13 and a regeneration flow rate of the regeneration hydraulic motor, computes a required first hydraulic pump revolution speed from a displacement of a first hydraulic pump 15 and a target assist flow rate of the first hydraulic pump, and selects a greater one of the required regeneration hydraulic motor revolution speed and the required first hydraulic pump revolution speed as a target revolution speed of an electric motor 14.

Abstract: It is an object of the present invention to provide a hydraulic drive system that effectively utilizes a hydraulic fluid accumulated in an accumulator to make it possible to achieve a substantial improvement in terms of efficiency for a work machine as a whole. A hydraulic drive system includes: a first hydraulic pump; a first hydraulic actuator driven by being supplied with a hydraulic fluid from the first hydraulic pump; a first line for supplying the hydraulic fluid from the first hydraulic pump to the first hydraulic actuator; a first pump flow adjustment device installed in the first line, the first pump flow adjustment device being configured to adjust; a first hydraulic accumulator for accumulating the hydraulic fluid delivered from the first hydraulic pump; and a first accumulation flow adjustment device configured to adjust the flow of the hydraulic fluid from the first hydraulic pump to the first hydraulic accumulator.

Abstract: A work machine has a controller which has an area limiting control section correcting the pilot pressures of pilot lines, a regeneration control section adjusting the flow rate of the hydraulic fluid caused to flow from a tank side line of an arm cylinder into a pump side line thereof between zero and a predetermined upper limit value, and a regeneration control switching section that issues an order to the regeneration control section to set the predetermined upper limit value to a first set value when the function of the area limiting control section is invalid and that issues an order to the regeneration control section to set the predetermined upper limit value to a second set value that is smaller than the first set value when the function of the area limiting control section is effective.

Abstract: A work machine including a front control section configured to calculate a limit command value for restricting an operation of a front work implement includes: for example, a bypass line that bypasses, for example, the proportional solenoid valve in, for example, the pilot line; for example, a bypass valve disposed in, for example, the bypass line; a switch configured to output a signal to turn on or off control by the front control section; an on/off determining part configured to determine whether the signal from the switch is an on signal that brings front control into an on state or an off signal that brings the front control into an off state; an open/close command part configured to generate an open/close command signal to open the bypass valve when the signal is determined to be the off/off signal.

Abstract: A hydraulic fluid energy regeneration apparatus of a work machine includes: a regeneration hydraulic motor driven by a return hydraulic fluid; a first hydraulic pump mechanically connected to the regeneration hydraulic motor; a second hydraulic pump that delivers a hydraulic fluid for driving a hydraulic actuator; a confluence line that causes the hydraulic fluid delivered from the first hydraulic pump to join the hydraulic fluid delivered from the second hydraulic pump; a first adjuster configured to adjust the flow rate of the hydraulic fluid of the first hydraulic pump; and a second adjuster configured to adjust the delivery flow rate of the second hydraulic pump.

Abstract: Provided is a work machine capable of regenerating a return hydraulic fluid from a hydraulic actuator while preventing a drag loss of a regeneration hydraulic motor and a hydraulic pump from increasing and preventing the regeneration efficiency of the regeneration hydraulic motor from decreasing. A controller 100 computes a required regeneration hydraulic motor revolution speed from a displacement of a regeneration hydraulic motor 13 and a regeneration flow rate of the regeneration hydraulic motor, computes a required first hydraulic pump revolution speed from a displacement of a first hydraulic pump 15 and a target assist flow rate of the first hydraulic pump, and selects a greater one of the required regeneration hydraulic motor revolution speed and the required first hydraulic pump revolution speed as a target revolution speed of an electric motor 14.

Abstract: A hydraulic system for a work machine includes a first hydraulic pump driving a swing hydraulic motor; a second hydraulic pumps driving a boom cylinder; a first pump displacement increase valve controlling a volume of the first hydraulic pump; a swing pilot pressure sensor detecting a swing operation amount; a boom raising pilot pressure sensor detecting a boom raising operation amount; and a controller controlling a control signal to the first pump displacement increase valve on the basis of the swing operation amount and the boom raising operation amount. The controller controls the control signal in such a manner that a delivery rate of the first hydraulic pump becomes higher as the swing operation amount is larger and an increasing rate of the delivery rate of the first hydraulic pump becomes lower as the boom raising operation amount is larger during a swing boom raising operation.

Abstract: The first engine speed or a work machine is higher than the minimum engine speed, and the second engine speed is higher than the first engine speed and lower than the maximum engine speed. The ratio of the change in the target engine speed to the change in the operation amount of the engine speed instructing device when the operation amount of the engine speed instructing device is changed from the operation amount for instructing the minimum speed to the operation amount for instructing the first engine speed is larger than the ratio of the change in the target engine speed to the change in the operation amount of the engine speed instructing device when the operation amount of the engine speed instructing device is changed from the operation amount for instructing the second engine speed to the operation amount for instructing the maximum speed.

Abstract: A hydraulic circuit (11) of a hydraulic excavator (1) is provided with a main hydraulic circuit (11A) including a boom cylinder (5D), a pilot hydraulic circuit (11B) for operating the boom cylinder (5D) and a recovery hydraulic circuit (11C) including an accumulator (29). In this case, the recovery hydraulic circuit (11C) is provided with a recovery control valve (31) that recovers pressurized oil discharged from the boom cylinder (5D) to the accumulator (29), a main supply control valve (34) for supplying pressurized oil accumulated in the accumulator (29) to the main hydraulic circuit (11A) and a pilot supply control valve (37) for supplying pressurized oil accumulated in the accumulator (29) to the pilot hydraulic circuit (11B).

Abstract: A work machine includes: control valves that control flows of a hydraulic operating oil supplied to actuators; operation lever devices that generate hydraulic signals to be output to the corresponding control valves according to an operation; solenoid proportional valves that reduce pressure of the hydraulic signals generated by the corresponding operation lever devices; and a front implement control section that controls the solenoid proportional valves. The work machine further includes: operation signal lines connected to the operation lever devices; signal input lines connected to the control valves; pressure reducing lines provided with the solenoid proportional valves; and selector valves that have a first position that interrupts connection of the operation signal lines and the pressure reducing lines and directly connects the operation signal lines to the signal input lines, and a second position that connects the operation signal lines to the signal input lines via the pressure reducing lines.

Abstract: A hydraulic energy regeneration system for a work machine for boosting a pressure of a return hydraulic fluid of a hydraulic cylinder and regenerating the hydraulic fluid, prevents a bottom pressure from reaching an overload relief set pressure and suppresses a changeover shock to ensure favorable operability.

Abstract: Provided is a construction machine allowing regeneration of a return hydraulic fluid at the time of both a boom raising operation and a boom lowering operation with a small number of valves, making it possible to secure a satisfactory operability at the time of both the boom raising operation and the boom lowering operation.

Abstract: An object of the present invention is to provide a working machine and a working machine monitoring system using the same which is capable of improving the accuracy in determining fuel property. The working machine is provided with an engine operation parameter acquisition module (1041) that acquires an engine operation parameter representing the operation state of an engine mounted on the working machine; a refueling time acquisition module (1011) that acquires a refueling time when the working machine is supplied with fuel; and a fuel property determination module (1014) that determines the property of the fuel based on a comparison result of the time when the engine operation parameter changes, with the refueling time.

Abstract: A hydraulic control system achieves a reduction in meter-out pressure loss in accordance with variation of a negative load acting on a hydraulic actuator. A hydraulic fluid discharged from the actuator flows through meter-out flow lines having variable restrictors. A load sensor detects the magnitude of a negative load applied to the actuator by an external force in the same direction as the operating direction of the actuator. A control device reduces the sum total of the opening areas of the variable restrictors in accordance with an increase in the magnitude of the negative load detected by the load sensor and the operation amount detected by the operation amount sensor when the load abnormality sensor does not detect any abnormality. When an abnormality is detected, it reduces the sum total of the opening areas to a predetermined value in accordance with the operation amount detected by the operation amount sensor.

Abstract: A construction machine management system in which a failure analysis or a failure-omen diagnosis of a machine body can be performed with a high degree accuracy and at a low cost is provided. In a machine body group of construction machines including at least one representative machine body having an engine control unit that detects a cumulative stress value of a diesel engine of the construction machine and a crankcase pressure sensor that detects a crankcase pressure, and at least one general machine body that has an engine control unit but does not have a crankcase pressure sensor, a center server performs a diagnosis of an omen of a failure state regarding the crankcase pressure of the general machine body based on correlation information between the cumulative stress value and the crankcase pressure obtained from the representative machine body and the cumulative stress value of the general machine body.

Abstract: Provided is a hydraulic drive system for a work machine configured with a single solenoid proportional valve for a regeneration circuit, wherein substantially the same actuator speed can be secured irrespective of whether or not hydraulic fluid discharged from a hydraulic actuator is regenerated for driving of another hydraulic actuator.

Abstract: Provided is a hydraulic control system for a construction machine, including: a control valve (31) for controlling supply and discharge of hydraulic fluid to and from an arm cylinder (4); an operation lever (6) for controlling the position of a spool of the control valve (31); a meter-out flow passage (34) for passing therethrough hydraulic fluid discharged from the arm cylinder; a variable restrictor (23a) provided in the meter-out flow passage; pressure sensors (41, 42) for detecting a magnitude of a negative load applied by an external force to the arm cylinder in a same direction as an actuation direction of the arm cylinder; and a controller (45) for reducing an opening area of the variable restrictor (23a) according to an increase in the magnitude of the negative load calculated with a detection value from the pressure sensors (41, 42).

Abstract: Disclosed is a hydraulic drive system capable of improving the fuel efficiency of a work machine by reducing the pressure loss and drag loss of a hydraulic pump. There are provided an electric motor M; a third pump P3 driven by the electric motor; a third pump hydraulic line L3 to which the delivered hydraulic fluid from the third pump is supplied; a third directional control valve V4 provided in the third pump hydraulic line, switch-operated by an arm operation device 19, and controlling the flow rate of the hydraulic fluid supplied to the arm cylinder 8 from the third hydraulic pump; and a controller 18 drive-controlling the electric motor, wherein the controller drives the third pump by the electric motor when a swing/arm combined operation is detected by pilot pressure sensors S6, S7, S10, S11.

Abstract: A hydraulic excavator (1) includes a controller (40) for generating, when the tip of a work implement (1A) is approaching a target surface (60) due to the pilot pressure output from an operating device (45a, 45b, 46a), a control signal for a boom cylinder (5) such that the tip of the work implement moves along the target surface and controlling the work implement (1A) by outputting the generated control signal to the flow control valve (15a) of the boom cylinder (5). The controller calculates the positional information of a finished shape (97) formed by the work implement, based on the topographic information input from a topographic measurement device (96) that measures the topography near the work machine and corrects the control signal based on the positional information of the finished shape such that the finished shape gets closer to the target surface.